# US 4,684,131 A · Graphite composite racquet with aramid core

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- Number: US 4,684,131 A
- Document ID: US4684131A
- Status: Granted
- Kind: A
- Application number: 06/788,441
- Filed: 1985-10-17
- Granted: 1987-08-04
- Earliest claimed: 1984-06-14
- Assignees: Ektelon
- Inventors: Raymond L. Mortvedt
- Web page: https://patentgrep.com/patent/US4684131A

## CPC

- A63B 49/10: made of non-metallic materials, other than wood
- A63B 60/54: with means for damping vibrations
- A63B 2209/023: Long, oriented fibres, e.g. wound filaments, woven fabrics, mats
- Y10S 273/07: Glass fiber
- Y10S 273/23: High modulus filaments
- A63B: APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT (apparatus for passive exercising, massage A61H)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

The present invention comprises a graphite composite racquet frame having a particular structure that provides internal and external shock absorption. The internal shock absorption is provided by a core material having high impact strength such as an aromatic aramid. External shock absorption is provided by a fiber reinforced plastic wrapping. The shock absorption elements allow graphite fibers to be used for construction of racquets which are commonly subject to a great deal of physical abuse such as racquetball racquets.

## Claims

### Claim 1

A throatless and wishbone shaped graphite composite racquet frame having a head, a neck and a handle, said frame comprising:
a core of aramid;
a layer of graphite fibers surrounding said core; and
a fiber glass wrapping positioned over said layer of graphite fiber, forming a composite thereby;
wherein the graphite fiber is cushioned by the aramid on the inside and the fiber glass wrap on the outside of the racquet frame,
said core of aramid, said layer of graphite fibers, and fiber glass wrapping being continuous throughout the head, neck and handle portions of the frame;
and a pair of opposite boron inserts in the neck portion of the racquet, said inserts positioned on opposite sides of the frame substantially parallel to each other to achieve higher stiffness and strength in the neck region without added weight or bulk, said boron inserts being positioned over said graphite layer and under said fiber glass wrapping.

### Claim 2 (depends on 1)

A racquet frame according to claim 1 which includes weighting means positioned in the frame at the head thereof to widen the sweet spot of the racquet.

### Claim 3 (depends on 1)

A racquet frame according to claim 1 wherein the boron inserts have a tensile strength of about 400,000 psi, compressive strength of about 500,000 psi, and a tensile modulus of about 30.times.10.sup.6 psi.

### Claim 4 (depends on 1)

A racquet frame according to claim 1 wherein the graphite fibers have a tensile strength of about 200,000 psi and a modulus of about 20.times.10.sup.6 psi, and having a strain ratio of 0.01 or greater.

### Claim 5 (depends on 1)

A racquet frame according to claim 1 in which the direction of the grain of the graphite fibers in each layer is at an angle to the longitudinal axis of the frame.

### Claim 6 (depends on 1)

a racquet frame according to claim 1 including an additional continuous graphite layer surrounding the first-mentions layer, said additional graphite layer extending through the head but not into the handle of said frame, said boron inserts being positioned between the first-mentioned and the additional graphite layers.